Previous research has indicated that heart rate, systolic blood pressure (BP), and indirect indices of cardiac contractile force show substantial elevations during shock avoidance and other stressful tasks which encourage active coping. Preliminary evidence also suggests that an individual's cardiovascular responses to such laboratory stressors are stable across time and across different types of behavioral stress. The proposed research will attempt to establish whether cardiovascular changes observed in young adults under lab stressors are similar to those observed under natural stress. In addition, other factors found to be significant in studies of borderline hypertension, including lability of rest BP, beta-adrenergic contributions to BP and cardiac performance, plasma renin activity, and personality factors, will be examined in relation to the subject's cardiovascular responses to stress in the field and the lab. Two types of studies will be used: 1) lab studies were stressful conditions mimic common natural events; 2) repeated lab and field monitoring of selected subjects whereby the same individual's responses under the two conditions can be compared. Naturalistic stressors used in the lab will include reaction time and mental arithmetic tasks in which active involvement is enhanced by money bonuses, speed pressure, competition with peers, or the presence of an evaluating observer. Besides these naturalistic stressors, subjects in repeated stress studies will be monitored during the shock avoidance task previously shown to provide the best differentiation between subjects high and low in heart rate reactivity to stress; pharmacological blockade of beta-adrenergic receptors will be performed during one lab session to provide a with-in subject index of beta adrenergic contributions to stress responses. Both lab and field studies will use systolic time intervals recorded by ear densitography, as well as heart rate and BP measures, to monitor cardiovascular changes; the former has potential for providing beat-by-beat tracking of cardiac performance and systolic BP changes during events such as college exams without requiring any initiating by the subject.